MuntyScruntfundle
Posts: 199
Joined: Fri Oct 27, 2017 11:14 pm

Reset switch.

Sat Dec 08, 2018 9:14 pm

Hi there.

I'm looking to put a reset switch on a bunch of pis. Model 3B+.

Looking at the header location there are two contacts, RUN and PEN.

My questions are:
1. I'm guessing RUN is the reset pin?
2. Does opening or closing the loop to ground set the reset state?
3. What does the PEN pin do?

Many thanks.

MuntyScruntfundle
Posts: 199
Joined: Fri Oct 27, 2017 11:14 pm

Re: Reset switch.

Sat Dec 08, 2018 9:18 pm

And I meant to add, of those that have tried this, what switch have you used?

I'm left in the situation where the switch will have to hang from the back of the board, less than ideal, but it's all I can do. I will need a small switch. I've ordered a few mini micro switches to test with but they're in-feasibly small, I don't think the soldering will be strong enough to last.

Any ideas for a source of small (ish) push switches?

Thanks.

klricks
Posts: 6071
Joined: Sat Jan 12, 2013 3:01 am
Location: Grants Pass, OR, USA
Contact: Website

Re: Reset switch.

Sat Dec 08, 2018 9:23 pm

MuntyScruntfundle wrote:
Sat Dec 08, 2018 9:14 pm
Hi there.

I'm looking to put a reset switch on a bunch of pis. Model 3B+.

Looking at the header location there are two contacts, RUN and PEN.

My questions are:
1. I'm guessing RUN is the reset pin?
2. Does opening or closing the loop to ground set the reset state?
3. What does the PEN pin do?

Many thanks.
The PEN is power enable used with HATs and such.

In order to add a reset you will need to connect a momentary type switch to RUN and to a ground from somewhere else on the board such as GPIO pin 6 or other ground pin.
Connecting RUN to ground will immediately halt the system in an unkind way of the RPi is running. When released then the RPi will reboot.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Stretch w/ Desktop OS.

Cornz
Posts: 2
Joined: Mon Feb 18, 2019 3:11 pm

Re: Reset switch.

Mon Feb 18, 2019 3:37 pm

Hi all.
UTTER pi beginner here.
I too am asking the question about the reset switch. My question is this.
Is there a way of resetting the pi, via a simple push switch but requiring no software if using the run pin to 0v is "unkind".
In what way is it "unkind" other than being crude. The only downside i can see is that if your pi is writing data then that data may be lost.
is there an alternative location for a "reset kludge", somewhere on the PSU section of the PCB. Or cutting a track then soldering the switch between the two points (obvs a push to break switch) which seems how the wall-warts do it with a switch in the usb cable. How is that less unkind than grounding the cpu reset pin?

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davidcoton
Posts: 3490
Joined: Mon Sep 01, 2014 2:37 pm
Location: Cambridge, UK

Re: Reset switch.

Mon Feb 18, 2019 4:26 pm

Reset is only "unkind" if the Pi is running. It will immediately stop the Pi, including any writes in progress to the SDCard or other mass storage. This can lead to corruption of the OS files, and failure to reboot or other strange problems.

Reset is fine as a way to restart a system that has been properly shut down (halted) but left with power on. There are also ways to use a GPIO input to shut down and restart the Pi. See the links in this post and the following one.
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fruitoftheloom
Posts: 18522
Joined: Tue Mar 25, 2014 12:40 pm

Re: Reset switch.

Mon Feb 18, 2019 4:30 pm

Cornz wrote:
Mon Feb 18, 2019 3:37 pm
Hi all.
UTTER pi beginner here.
I too am asking the question about the reset switch. My question is this.
Is there a way of resetting the pi, via a simple push switch but requiring no software if using the run pin to 0v is "unkind".
In what way is it "unkind" other than being crude. The only downside i can see is that if your pi is writing data then that data may be lost.
is there an alternative location for a "reset kludge", somewhere on the PSU section of the PCB. Or cutting a track then soldering the switch between the two points (obvs a push to break switch) which seems how the wall-warts do it with a switch in the usb cable. How is that less unkind than grounding the cpu reset pin?

http://www.uugear.com/witty-pi-realtime ... pberry-pi/
adieu

My other Computer is an Asus CS10 ChromeBit

PhatFil
Posts: 846
Joined: Thu Apr 13, 2017 3:55 pm
Location: Oxford UK

Re: Reset switch.

Mon Feb 18, 2019 4:53 pm

One unsafe method of shutting down is pretty much as bad as another, and your always best served checking the activity led has stopped flashing for a good few seconds before committing to any unsafe shutdown method.


Less dependable than hard wired options you can use remote network connections or other wireless protocols.
a ssh session from your phone or pc can be used to log in and execute a shutdown or reboot safely.

or if you prefer a gui for the phone connection? host a mqtt broker on your pi and install a mqtt app on your phone. publish a shutdown topic/payload message from your phone app and run a script on your pi to sit subscribing to the topic and shutdown safely when received.

check out the variouse ble luggage/key/child finder device hacks for a dedicated wireless trigger. amazon dash buttons while hackable are not very green or cheap being a single use device with a built in battery that requires device destruction to change.

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